Summary:
In this study, we compare the responses of downhole magnetometric resistivity (MMR) and downhole electric resistance tomography (ERT) due to changes in electric resistivity consecutive to CO2 injection in a saline aquifer. The results indicate that a smaller volume of CO2 is detectable with MMR, for noise levels inferred from field data. This is attributed to the fact that the MMR method is sensitive to current density variations and not to absolute values of resistivity. Consequently, the MMR response is not affected by the problem of noise in conductive media, as is the case for ERT (very weak electrical potential in conductive environments). Moreover, sensitivity maps show that the sensitivity patterns have broader extents for MMR.